A British endurance cyclist has smashed the Guinness World Record for the fastest circumnavigation of the planet on a bicycle, riding 18,000 miles (29,000km) in under 80 days.

Mark Beaumont cycled for 18 hours a day and burned more than 9,000 calories every 24 hours as he crossed Poland, Russia, Mongolia, China, Australia and the United States.

"It's literally about riding to the next horizon," the Scotsman said on Monday after completing his marathon ride under the Arc de Triomphe in Paris. "I've barely walked for two-and-a-half months."

A crash in Russia on the ninth day in which he broke a tooth and injured his elbow nearly ended a ride that he said had taken him to a "mental depth" he had never before experienced.

"It's just the sleep deprivation. It's after weeks and weeks and weeks, it's just the long, long hours you spend in your head, you know, really battling. And you just need to decide you're never going to stop," he said.

He completed the ride in 78 days, 14 hours and 40 minutes. The record was previously held by New Zealander Andrew Nicholson, who in 2015 managed the feat in 123 days.

A Guinness World Record adjudicator handed the cyclist two world record certificates - one for the round-the-world record, the other for the furthest distance cycled in a single month.